Due to advance of the telecommunication technology, the local wireless system and the mobile phone are provided with in-built antenna assemblies respectively for transmitting and receiving signals from far and nearby.
FIG. 1 shows a conventional mobile phone 2 is shown to include an upper casing 6, a lower casing 8, an input keypad 12, and a printed circuit board 14. The upper casing 6 has an LCD panel 10, and is formed with a plurality of input keys 602.
The printed circuit board 14 generally includes several complicated circuits, chipsets, and other electronic components for different functions. The printed circuit board 14 is disposed below the keypad 12. The keypad 12 is formed with a plurality of conductive pads 1202 respectively aligned with the input keys 602 of the upper casing 6. Depression of an input key 602 via an actuator (not shown) results in a contact between the respective conductive pad 1202 and the respective circuit, thereby sending a signal to the signal-processing module (not shown).
As a rule, the mobile phone 2 is provided with an antenna assembly according to the requirement for transmitting and receiving signals. For communication with a base station, an antenna assembly 3 is fabricated on the top portion of the printed circuit board 14. For communication with the local wireless system, for example WLAN, another antenna assembly 4 (hence WLAN antenna assembly) is fabricated on the lower portion of the printed circuit board 14. As shown in FIG. 1, the antenna assembly 4 has a F-shaped configuration and includes a radiating metal strip having a main strip section 402 mounted on the printed circuit board 14 adjacent to the periphery thereof, a feeding strip section 404 for coupling to the signal-processing module (not shown) and a grounding strip section 406 for grounding purposes.
Moreover, the upper and lower surface of the printed circuit board 14 defines a naked space 16 for receiving the main strip section 402, the feeding strip section 404 and the grounding strip section 406. Since the naked space is free from circuits and is defined by a portion of the FR 4 standard laminates, which as a whole serves as the major medium for forming the printed circuit board 14 once the circuits are fabricated thereon. Enlargement of the distance between the main strip section 402 and the conductive layer at a lower elevation in the printed circuit board 14 can result in decrease of the Q value, thereby enhancing the storage capacity of the antenna assembly and consequently permitting the latter to possess a wider band of operating frequency.
As a matter of fact, due to the presence of the naked space 16 in the printed circuit board, it makes the manufactures of the electronic device more difficult to design the complicated circuit paths on the remaining space of the printed circuit board. Since the mobile phone (each electronic device) is under the trend toward the compact size, formation of the aforesaid naked space 16 results in waste of precious space in the printed circuit board. In addition, the manufacturers of the antenna assembly aggressively want to widen the distance between the main strip section and the conductive layer disposed at a lower elevation.
Therefore, the main object of the present invention is to provide an antenna assembly for solving the aforesaid problems.